Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$144.64	4.711%	$151.454	$151.45	$151.45	$151.50
Purchase #2	$89.56	11.410%	$99.7788	$99.78	$99.80	$99.80
Purchase #3	$43.52	10.335%	$48.0178	$48.02	$48.00	$48.00
Purchase #4	$181.70	11.863%	$203.2551	$203.26	$203.25	$203.30
Purchase #5	$42.72	10.690%	$47.2868	$47.29	$47.30	$47.30
Purchase #6	$144.25	5.407%	$152.0496	$152.05	$152.05	$152.00
Purchase #7	$207.73	11.449%	$231.513	$231.51	$231.50	$231.50
7 purchase totals =	$854.12		$933.3551	$933.36	$933.35	$933.40